docs(@projects/@magic-civilization): 📝 p3-18 — P5a done, P6-core done; scope P5b (rendered-movement embark, single-source via bridge)

P5a (dead GDScript embark UI) and P6-core (ford integration proof) landed. P5b
(rendered UI embark) scoped: the rendered state is hybrid (GDScript GameState/Player
+ Rust GdGameState bridge); the single-source path is a GdGameState #[func]
exposing the Rust-computed EmbarkLevel, threaded into pathfinder.gd — dylib-gated
(build-gdext.sh works) + GUT. P6-full demo is confirmatory over the integration proof.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.project/objectives/p3-18-water-crossing-embark-transport.md

@@ -94,21 +94,28 @@ two-tier Civ model on the existing tree (`public/resources/techs/naval.json`):
   target-selection changes that touch 1UPT assumptions (rare for a tier-9 hull;
   the prune already handles hull-death). AI does not yet load units onto transports
   (negligible value — tier-9 hull the AI rarely builds; embark covers crossing).
-- [ ] **P5 — GDScript pathfinder mirror + FFI trim. FUNCTIONALLY REQUIRED.** The
-  rendered game moves units via `world_map.gd → PathfinderScript.find_path`
-  (`pathfinder.gd`), NOT the Rust pathfinder — so embark currently works **headless
-  only** (GdPlayerApi → Rust `process_one_move`), and a human playing the UI cannot
-  embark until this lands. Either plumb the owner's `EmbarkLevel` into
-  `pathfinder.gd::_is_passable`/`find_path`/`find_path_with_fog` + their callers,
-  or (Rail-1 preferred) route world_map movement through the Rust pathfinder. Also
-  drop the vestigial embark inputs from `legal_actions_for`/`can_invoke` + GDScript
-  callers. *(Feasible locally — the gdext crate is `magic-civ-physics-gdext` and
-  `cargo check -p magic-civ-physics-gdext` is green in ~38s; the earlier "cargo
-  resolver panic" was a wrong `-p gdextension-api` (that name is a crates.io godot
-  dep, not our crate). Build the dylib via `build-gdext.sh`; GUT verifies.)*
-- [ ] **P6 — end-to-end.** A headless 1v1 (both sides driven) reaches a decisive
-  `game_over` by crossing water to capture the enemy capital — the demo that
-  motivated this objective.
+- [x] **P5a — remove dead GDScript explicit-embark UI.** ✅ (`bb6eb6ee5`) Deleted
+  the dangling `embark_pressed`/`disembark_pressed` signals, ACTION_SIGNAL_MAP
+  entries + emit cases (`unit_panel.gd`) and the signal connections + handlers
+  (`world_map.gd`) that P3b orphaned. No dangling refs; no GUT test referenced them.
+  Auto-embark is the only embark model across Rust **and** the GDScript UI.
+- [ ] **P5b — rendered-movement embark (functionally required for UI play).** The
+  rendered game moves via `world_map.gd → PathfinderScript.find_path` (GDScript
+  `pathfinder.gd`), so embark works **headless only** today. State is hybrid
+  (GDScript `GameState`/`Player.researched_techs` + a Rust `GdGameState` bridge). To
+  stay single-source (no re-hardcoding tech ids in GDScript — that would undo P1b),
+  add a `GdGameState` `#[func]` returning the Rust-computed `EmbarkLevel` (via
+  `TechWeb::embark_level`), thread it into `pathfinder.gd::_is_passable`/`find_path`/
+  `find_path_with_fog` + the `world_map.gd` callers; also drop the vestigial embark
+  inputs from `legal_actions_for`/`can_invoke`. **Rail-1 alternative (preferred
+  long-term):** route rendered movement through the Rust pathfinder — larger,
+  overlaps the standing `pathfinder.gd` port debt. *(Dylib-gated: `build-gdext.sh`
+  works — gdext crate is `magic-civ-physics-gdext`, `cargo check` green in ~38s — + GUT.)*
+- [ ] **P6 — end-to-end (full demo).** P6-core ✅ (`4a81f0d16`,
+  `teched_army_fords_open_ocean_to_far_landmass`) proves the army crosses water
+  deterministically. P6-full (a headless 1v1 to a decisive `game_over` by crossing
+  water to take the enemy capital) remains — needs the dylib rebuilt + a naval-tech
+  scenario; confirmatory over the integration proof.
 
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